-LRB- CNN -RRB- -- Top aides to President Obama on Sunday signaled that some U.S. troops could start coming home from Afghanistan as soon as July 2011 , but most would likely remain there for several years .

In appearances on all the major talk shows , Cabinet officials and military advisers clarified the president 's position after he walked a political tightrope by announcing he will send 30,000 more troops to Afghanistan and that some will start coming home in 19 months .

National Security Adviser Gen. James Jones told CNN 's `` State of the Union '' that the July 2011 start of withdrawal was `` not a cliff , it 's a ramp '' for beginning to turn over security responsibility to Afghan forces .

Noting the U.S. strategic interests in the region , including nuclear power Pakistan next door , Jones said : `` We 're going to be in the region for a long time . ''

Gen. David Petraeus , the head of U.S. Central Command , said on `` FOX News Sunday '' that Obama 's strategy `` does n't trigger a rush to the exits , '' while Defense Secretary Robert Gates told CBS ' `` Face the Nation '' that `` there is n't a deadline . ''

`` What we have is a specific date on which we will begin transferring responsibility for security district by district , province by province in Afghanistan to the Afghans , '' Gates said .

The challenge has been to meet the need cited by military leaders for more troops and resources to wipe out terrorist networks in Afghanistan and to help the Afghan government overcome the Taliban insurgency , while satisfying the Democratic Party 's liberal base , which opposes the deployment of more troops .

Gates explained the rationale for sending more forces on ABC 's `` This Week , '' saying the Afghan-Pakistani border is `` the epicenter of extremist jihad . ''

`` And al Qaeda has close relationships with the Taliban in Afghanistan , and they have very close relationships with the Taliban in Pakistan , '' Gates continued . `` The Taliban in Pakistan have been attacking Pakistani civilians , Pakistani government officials , military officials , trying to destabilize the government of Pakistan . ''

Any success by the Taliban in either Afghanistan or Pakistan benefits al Qaeda , Gates said , adding that `` any safe haven on either side of the border creates opportunities for them to recruit , get new funds and do operational planning . ''

`` And what 's more , the Taliban revival in the safe havens in western Pakistan is a lesson to al Qaeda that they can come back , if they are provided the kind of safe haven that the Taliban were , '' Gates said .

In addition , Gates warned on NBC 's `` Meet the Press '' that U.S. casualties `` will probably continue to grow '' as troops take on Taliban strongholds . However , Gates rejected a comparison to the Soviet Union 's decision in 1985 to send more troops to bolster its occupation of Afghanistan , which ended in failure less than two years later .

`` The parallel just does n't work , '' Gates said . `` The reality is the Soviet Union invaded Afghanistan . They killed a million Afghans . They made 5 million refugees out of Afghanis . ''

In addition , he said , the Soviets acted unilaterally , while the U.S.-led mission in Afghanistan involves 42 countries with a mandate from NATO .

In Congress , Republicans generally backed Obama 's deployment plan but complained that announcing the start of a withdrawal was a signal to the enemy of a compromised commitment .

Sen. John McCain of Arizona , the unsuccessful GOP presidential candidate last year , told NBC 's `` Meet the Press '' that a strategy must be flexible to succeed , rather than limited by a set timetable .

On `` FOX News Sunday , '' Sen. Dick Durbin , the chamber 's second-ranking Democrat , called the July 2011 start of a withdrawal a necessary signal to Afghan President Hamid Karzai .

According to Durbin , Obama 's message to Karzai was : `` We 're not going to make Afghanistan a protectorate of the United States . You have to change your government . You have to show that you are willing to stand up and fight for your own country . ''

`` I think that message is long overdue , '' Durbin said .

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Obama aides hit Sunday talk shows to discuss nuances of Afghan troop withdrawal

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National security adviser says July 2011 is `` not a cliff , it 's a ramp '' for starting pullout

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Defense secretary tells CBS `` there is n't a deadline '' to get troops out

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Administration trying to wipe out terrorist network while satisfying liberal base